Mehler, A. H., in “A Symposium on Amino Acid Metabolism”, edit. by McElroy, W. D., and Glass, H. B. (The Johns Hopkins Press, Baltimore, 1955).

The structure of Protonix is very similar to that of a compound (known as compound 12) that is described in the earlier Altana patent, but with a different substitution on the pyridine ring.